In normal operation, a machine tool, such as a lathe, produces waste material that should be removed from the workpiece being machined. In these cases, the waste material that is removed from the workpiece is generally removed in various sizes including small pieces that are generally referred to as chips. These chips mix with the coolant/cutting oil (hereinafter referred to as cutting fluid) used in the machining process. The cutting fluid can be used for cooling, wash down and/or lubrication, for example. This mixture of cutting fluid and cutting chips enters the conveyor used for removing the chips from the cutting fluid. The cutting chips are thus conveyed from the receiving position to a discharge position.
The cutting fluid drains through the conveyor to the machine tool oil/coolant reservoir. Some of the chips that are mixed with the cutting fluid also pass into the machine's oil/coolant reservoir with the cutting fluid. These chips eventually build up in the machine oil/coolant reservoir and require manual intervention to clean them out, because the cutting fluid in the reservoir is generally re-circulated for further use. Thus, before the cutting fluid can be recirculated and reused, the waste material produced during the operation of the machine tool first has to be removed.
Hinge belt conveyors are widely used to convey the chips away from the cutting fluid. This type of conveyor is the most simple of all conveyors on the market, and is widely used throughout the industry. This is a very versatile product in that it is capable of taking any chip shape or size, but has generally one major drawback in that it often does not offer any filtration. This results in small chips passing through the conveyor into the cutting fluid tank which then means that the machine operator has to perform regular maintenance to clean out the tank (duration depending on the specific application).
However, filtering chip conveyors also exist and self-cleaning scraper conveyors are an example of these kinds of conveyors. They can filter out particles (chips) down to a particle size of around 500 μm (0.5 mm). The minimum dimension of the particles which can be filtered out of the fluid is also referred to as the filtration level. These kinds of conveyors, such as the one disclosed in WO2004/054756, typically use a self-cleaning filter box to prevent small chips (larger than the filtration level of the filter screens used) from passing out of the cutting fluid tank and being cycled back into the machine tool. One problem with such self-cleaning scraper conveyors is that they do not generally filter long chips well, especially long chips having a smallest dimension (thickness) similar to the size of the openings in the filter material. Chips are liable to become wedged in the weave of typical woven filtration meshes, and are difficult for the scrapers to dislodge. The mesh becomes clogged, and the fluid flow through the screen, and thereby the filtration performance, is markedly reduced. This is one of the reasons why self-cleaning scraper conveyors are commonly supplemented with a filter drum. This combination is better suited to applications in which a wide variety of various chip sizes and shapes are produced and in which filtration is needed.
Machines today are capable of many types of machining processes and thus produce a wide range of chip types and shapes. The currently available solutions are either inefficient (with no or poor filtration) or very expensive, due to the complexity of the drum filter and self-cleaning scraper conveyor arrangements required.
It is the aim of the present invention to overcome the problems identified above. More specifically, the aim is to provide a solution for filtering chip conveyors so that a high fluid through-flow can be obtained, while at the same time allowing filtration levels down to 50 μm or even lower.